let str = 'http://kenput.oss-cn-shenzhen.aliyuncs.com/file/20200723161617321245.jpg?Expires=1910852178&OSSAccessKeyId=LTAI4GFRXofLCL7ife3xvQY9&Signature=Q+OTF9RL1T2+zTvB/5IJMXaUMC0=';
let reg = /\S+.(jpg|jpeg)/g;
let result = str.match(reg)[0];
console.log(result);